1. Field of the Invention
The invention relates to the field of control switches of the type used in control panels and switch stations in an industrial environment.
2. Description of the Prior Art
In the field of digital office equipment, touch-actuated switching panels have been developed to replace traditional key-operated panels. These newer panels commonly involve several thin sheets of an insulating material such as Mylar. A spacing sheet is used between two other sheets on which conductive areas have been formed by screen printing or other deposition processes. The spacing sheet contains openings to allow the conductive areas on the spaced apart sheets to contact one another when pushed together at the touch of an operator. Such pressure sensitive switching panels have their functional labels arranged in patterns and arrays resembling keyboards, yet such panels are flush with the surface of the control panel or equipment utilizing them. Such panels have the advantage of sealed contacts, but in an industrial environment lack the tactility or other form of feedback to the human operator that is provided by traditional industrial controls. Such membraneous, touch sensitive switching panels are by the nature of their construction more readily adapted to arrays and have not provided suitable individual switches that can be located apart from control panels.
In membrane switches of the type described, there is a small amount of air trapped between the conductive areas that meet when one of the membranes is deflected. With this deflection the air pressure is increased, as there is nowhere for the air to escape. To provide better switching action in membrane arrays, channels have been formed in the spacer so that air may be cross-vented from one set of switch contacts to another. There has not been a comparable development of a breather for an individual switch of the type disclosed in the copending application of Long et al filed concurrently herewith and entitled "Industrial Membrane Switch," and for an individual switch of the type disclosed in the copending application of Fillus et al filed concurrently herewith and entitled "Illuminated Industrial Membrane Switch."